U.S. patent application number 17/669833 was filed with the patent office on 2022-09-22 for aviation system.
The applicant listed for this patent is JAPAN AEROSPACE EXPLORATION AGENCY, SUBARU CORPORATION. Invention is credited to Hiromitsu Miyaki, Takao Okada, Hiroyuki Tsubata.
Application Number | 20220299552 17/669833 |
Document ID | / |
Family ID | 1000006194571 |
Filed Date | 2022-09-22 |
United States Patent
Application |
20220299552 |
Kind Code |
A1 |
Tsubata; Hiroyuki ; et
al. |
September 22, 2022 |
AVIATION SYSTEM
Abstract
According to one implementation, an aviation system 100 includes
electric field sensors 112 and a ground system 114 including a
computer configured to communicate with each of the electric field
sensors 112. The computer is configured to: acquire electric field
intensities from the electric field sensors 112 respectively, and
generate a first electric field distribution on a ground surface 16
based on the electric field intensities; derive a matrix; derive a
pseudo inverse matrix of the matrix; derive an electric charge
distribution on the horizontal plane by multiplying the pseudo
inverse matrix by the first electric field distribution on the
ground surface 16; and derive a second electric field distribution
on a flight path based on the electric charge distribution. The
first electric field distribution on the ground surface 16 is
derived by multiplying the matrix by electric charges temporarily
set on a horizontal plane at a predetermined altitude.
Inventors: |
Tsubata; Hiroyuki; (Tokyo,
JP) ; Miyaki; Hiromitsu; (Tokyo, JP) ; Okada;
Takao; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUBARU CORPORATION
JAPAN AEROSPACE EXPLORATION AGENCY |
Tokyo
Tokyo |
|
JP
JP |
|
|
Family ID: |
1000006194571 |
Appl. No.: |
17/669833 |
Filed: |
February 11, 2022 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 29/0892 20130101;
G01R 29/0807 20130101; G01R 29/0878 20130101 |
International
Class: |
G01R 29/08 20060101
G01R029/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2021 |
JP |
2021-045045 |
Claims
1. An aviation system comprising: electric field sensors; and a
ground system including a computer configured to communicate with
each of the electric field sensors, wherein the computer is
configured to: acquire electric field intensities from the electric
field sensors respectively, and generate a first electric field
distribution on a ground surface based on the electric field
intensities; derive a matrix, the first electric field distribution
on the ground surface being derived by multiplying the matrix by
electric charges temporarily set on a horizontal plane at a
predetermined altitude; derive a pseudo inverse matrix of the
matrix; derive an electric charge distribution on the horizontal
plane by multiplying the pseudo inverse matrix by the first
electric field distribution on the ground surface; and derive a
second electric field distribution on a flight path based on the
electric charge distribution.
2. The aviation system according to claim 1, wherein the computer
is further configured to: smooth the derived electric charge
distribution; derive a third electric field distribution on the
ground surface based on the smoothed electric charge distribution;
derive a proportional constant which is a ratio between the first
electric field distribution on the ground surface and the third
electric field distribution on the ground surface; multiply the
smoothed electric charge distribution by the proportional constant;
and derive the second electric field distribution on the flight
path based on the electric charge distribution which has been
multiplied by the proportional constant.
3. An aviation method comprising: acquiring electric field
intensities from electric field sensors respectively by a computer
included in a ground system communicating with each of the electric
field sensors, and generate a first electric field distribution on
a ground surface based on the electric field intensities; deriving
a matrix, the first electric field distribution on the ground
surface being derived by multiplying the matrix by electric charges
temporarily set on a horizontal plane at a predetermined altitude;
deriving a pseudo inverse matrix of the matrix; deriving an
electric charge distribution on the horizontal plane by multiplying
the pseudo inverse matrix by the first electric field distribution
on the ground surface; and deriving a second electric field
distribution on a flight path based on the electric charge
distribution.
4. The aviation method according to claim 3, wherein the derived
electric charge distribution is smoothed; a third electric field
distribution on the ground surface is derived based on the smoothed
electric charge distribution; a proportional constant which is a
ratio between the first electric field distribution on the ground
surface and the third electric field distribution on the ground
surface is derived; the smoothed electric charge distribution is
multiplied by the proportional constant; and the second electric
field distribution on the flight path is derived based on the
electric charge distribution which has been multiplied by the
proportional constant.
Description
CROSS REFERENCES 10 RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2021-045045, filed on
Mar. 18, 2021; the entire contents of which are incorporated herein
by reference.
FIELD
[0002] Implementations described herein relate generally to an
aviation system and an aviation method.
BACKGROUND
[0003] Conventionally, the technology of avoiding a lightning
strike by ion emission has been examined. For example, a lightning
strike preventive system by which ion attached to fog by causing
corona discharge is emitted from the ground to form an ion cloud,
and thereby it is attempted to avoid a lightning strike direct to
the ground is described in Japanese Patent Application Publication
JP 1992 (H04)-071197.
[0004] A lightning strike may arise not only to a facility on the
ground but to an aircraft. An aircraft is a conductor, and
therefore a lightning strike whose trigger is an aircraft often
arises since an electric field in a space under a thundercloud
concentrates on the aircraft. Accordingly, it is desired to develop
the technology of reducing a lightning strike on an aircraft.
[0005] For example, it may be considered that a position at which a
thundercloud appears is predicted so that a flight path which can
avoid the thundercloud can be derived. However, it is difficult to
correctly predict a position at which a lightning strike whose
trigger is an aircraft arises, and a position of a thundercloud may
differ from an actual position of the lightning strike. It is known
that a position of a lightning strike has great influence of an
electric field on a flight path of an aircraft. However, there is
no effective means to appropriately estimate an electric field in a
wide range, such as a flight path.
[0006] Accordingly, an object of the present invention is to
provide an aviation system and an aviation method which can reduce
influence of a lightning strike on an aircraft.
SUMMARY OF THE INVENTION
[0007] In general, according to one implementation, an aviation
system includes electric field sensors and a ground system
including a computer configured to communicate with each of the
electric field sensors. The computer is configured to: acquire
electric field intensities from the electric field sensors
respectively, and generate a first electric field distribution on a
ground surface based on the electric field intensities; derive a
matrix; derive a pseudo inverse matrix of the matrix; derive an
electric charge distribution on the horizontal plane by multiplying
the pseudo inverse matrix by the first electric field distribution
on the ground surface; and derive a second electric field
distribution on a flight path based on the electric charge
distribution. The first electric field distribution on the ground
surface is derived by multiplying the matrix by electric charges
temporarily set on a horizontal plane at a predetermined
altitude.
[0008] The computer may be further configured to: smooth the
derived electric charge distribution; derive a third electric field
distribution on the ground surface based on the smoothed electric
charge distribution; derive a proportional constant which is a
ratio between the first electric field distribution on the ground
surface and the third electric field distribution on the ground
surface; multiply the smoothed electric charge distribution by the
proportional constant; and derive the second electric field
distribution on the flight path based on the electric charge
distribution which has been multiplied by the proportional
constant.
[0009] Further, according to one implementation, an aviation method
includes: acquiring electric field intensities from electric field
sensors respectively by a computer included in a ground system
communicating with each of the electric field sensors, and generate
a first electric field distribution on a ground surface based on
the electric field intensities; deriving a matrix; deriving a
pseudo inverse matrix of the matrix; deriving an electric charge
distribution on the horizontal plane by multiplying the pseudo
inverse matrix by the first electric field distribution on the
ground surface; and deriving a second electric field distribution
on a flight path based on the electric charge distribution. The
first electric field distribution on the ground surface is derived
by multiplying the matrix by electric charges temporarily set on a
horizontal plane at a predetermined altitude
[0010] The aviation method may include the following steps. The
derived electric charge distribution is smoothed. A third electric
field distribution on the ground surface is derived based on the
smoothed electric charge distribution. A proportional constant
which is a ratio between the first electric field distribution on
the ground surface and the third electric field distribution on the
ground surface is derived. The smoothed electric charge
distribution is multiplied by the proportional constant. The second
electric field distribution on the flight path is derived based on
the electric charge distribution which has been multiplied by the
proportional constant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] In the accompanying drawings:
[0012] FIG. 1 explains the relationship between a flight path and
an electric field;
[0013] FIG. 2 shows a schematic configuration of the aviation
system;
[0014] FIG. 3 is a block diagram showing a schematic configuration
of the ground system;
[0015] FIG. 4 is a flow chart showing a flow of electric field
deriving processing;
[0016] FIG. 5 explains the processing in the matrix deriving
part;
[0017] FIG. 6 explains the processing in the matrix deriving
part;
[0018] FIG. 7 explains the processing in the matrix deriving
part;
[0019] FIG. 8 explains an example of calculation in the electric
field deriving processing;
[0020] FIGS. 9A to 9D explain an example of calculation in the
electric field deriving processing;
[0021] FIG. 10A and FIG. 10B show a schematic configuration of the
aircraft; and
[0022] FIG. 11A and FIG. 11B explain the processing by the attitude
control part.
DETAILED DESCRIPTION
[0023] Hereinafter, a preferred implementation of the present
invention will be described in detail with reference to the
accompanying drawings. The sizes, materials, other concrete
numerical values, and the like shown in the implementation are only
exemplification for making understanding of the invention easy, and
do not limit the present invention as long as no particular comment
is made. Note that, the same signs are attached to elements having
the same function and/or configuration substantially in the present
specification and drawings, and thereby duplicated explanation
thereof is omitted. Illustration of elements which are not directly
related to the present invention is also omitted.
(Aviation System)
[0024] An aircraft is desirable to fly a flight path away from a
thundercloud in order to avoid a lightning strike. Therefore, an
aviation system predicts a position at which a thundercloud
appears, and derives a flight path which can avoid the
thundercloud. It is known that a position at which a lightning
strike whose trigger is an aircraft arises has great influence of
not only a thundercloud on a flight path of the aircraft but an
electric field generated due to the thundercloud.
[0025] Hereinafter, the influence on an aircraft is considered with
equivalently replacing an electric charge distribution in the whole
thundercloud with an electric charge distribution in a cloud
bottom. Concretely, electric charges equivalent to those
distributed perpendicularly and horizontally in a thundercloud is
virtually set up as an electric charge distribution in a cloud
bottom so that an electric field, in a space below the cloud bottom
in the vertical direction, generated by the electric charge
distribution in the cloud bottom may become equal to that generated
by the electric charge distribution in the whole thundercloud.
[0026] FIG. 1 explains the relationship between a flight path 14
and an electric field. In the example of FIG. 1, there are two
cloud bottoms 10 in the sky. It is assumed that one cloud bottom
10a is charged in the positive polarity side while the other cloud
bottom 10b is charged in the negative polarity side. In this case,
equipotential surfaces 12 as shown in FIG. 1 are formed due to the
cloud bottoms 10a and 10b.
[0027] When an aircraft 110 flies along a flight path 14, shown
with a broken line, in the above-mentioned electric field, the
aircraft 110 is influenced by the electric field generated by the
cloud bottoms 10a and 10b. For example, the aircraft 110 is
influenced by the electric field as shown with solid arrows in FIG.
1 at respective points on the flight path 14. In such a case, a
lightning strike may arise due to the aircraft 110 as a trigger
depending on the sizes and directions of the electric field.
[0028] Here, it may be considered that the electric charge
polarization of the aircraft 110 itself is calculated, and an
electric field at a flight position of the aircraft 110 is
estimated by the aviation system. However, the estimated electric
field is only one near a current flight position, and an electric
field cannot be grasped over the whole future flight path 14 of the
aircraft 110.
[0029] Accordingly, the aviation system acquires an electric field
distribution 18 on a ground surface 16, and estimates, based on the
electric field distribution 18, an electric charge distribution 20
in case of assuming that electric charges originally distributed
over a whole thundercloud are equivalently distributed only in a
cloud bottom 10. Then, the aviation system estimates an electric
field distribution 22 along the flight path 14 by electrostatic
analysis of the estimated electric charge distribution 20. In this
way, a high-precision lightning protection system can be
constructed.
[0030] FIG. 2 shows a schematic configuration of the aviation
system 100. The aviation system 100 includes an aircraft 110,
electric field sensors 112 disposed on the ground and a ground
system 114 consisting of circuitry disposed on the ground. Although
a passenger aircraft is exemplified as the aircraft 110 here,
various machines which fly in the atmosphere can be adopted.
(Electric Field Sensor 112)
[0031] Each electric field sensor 112 is installed apart from
another electric field sensor 112 by a predetermined distance (for
example, a few hundred meters) in a desired region on the ground
surface 16, e.g., around an airstrip where influence by lightning
is large. Each electric field sensor 112 may be a rotary type
electric field measuring instrument (field mill) or the like, and
can measure electric field intensity at least at a point at which
the electric field sensor 112 is located. Each electric field
sensor 112 can also transmit measured electric field intensity to
the ground system 114.
(Ground System 114)
[0032] FIG. 3 is a block diagram showing a schematic configuration
of the ground system 114. The ground system 114 is composed of a
computer including a central processing unit (CPU), a read-only
memory (ROM) storing programs and the like, a random access memory
(RAM) as a work area and the like. The ground system 114
communicates with each of the electric field sensors 112 and the
aircraft 110. The ground system 114 functions as an information
acquisition part 120, a matrix deriving part 122, a pseudo inverse
matrix deriving part 124, an electric charge distribution deriving
part 126, an electric field distribution deriving part 128, and an
information transmission part 130 by collaborating with programs.
Here, configuration related to the lightning strike avoidance which
is an object of the present implementation will be described while
description about configuration unrelated to the present
implementation is omitted.
[0033] FIG. 4 is a flow chart showing a flow of electric field
deriving processing. In information acquisition processing S100,
the information acquisition part 120 acquires electric field
intensities from the electric field sensors 112 respectively to
generate the electric field distribution 18 on the ground surface
16. In matrix deriving processing S102, the matrix deriving part
122 derives a coefficient matrix which becomes the electric field
distribution 18 on the ground surface 16 by being multiplied by
electric charges temporarily set on a cloud bottom surface
(horizontal plane) at a predetermined altitude. In pseudo inverse
matrix deriving processing S104, the pseudo inverse matrix deriving
part 124 derives a pseudo inverse matrix corresponding to the
coefficient matrix.
[0034] Then, in electric charge distribution deriving processing
S106, the electric charge distribution deriving part 126 derives
the electric charge distribution 20 on the cloud bottom surface by
multiplying the pseudo inverse matrix by the electric field
distribution 18 on the ground surface 16. In electric field
distribution deriving processing S108, the electric field
distribution deriving part 128 derives the electric field
distribution 22 on the flight path 14 based on the electric charge
distribution 20. In information transmission processing S110, the
information transmission part 130 transmits, to the aircraft 110,
the electric field distribution on the flight path 14 of the
aircraft 110. Hereinafter, the respective processing will be
described in detail.
(Information Acquisition Processing S100)
[0035] The information acquisition part 120 acquires electric field
intensities from the electric field sensors 112 respectively. The
information acquisition part 120 relates the acquired electric
field intensities to the known positions of the electric field
sensors 112 respectively to generate the electric field
distribution 18 on the ground surface 16.
[0036] Meanwhile, the information acquisition part 120 acquires the
flight path 14 along which the predetermined aircraft 110 is
planned to fly during predetermined time. The information
acquisition part 120 also acquires positions, heights, and sizes of
clouds (thunderclouds) from an observatory.
(Matrix Deriving Processing S102)
[0037] FIG. 5 to FIG. 7 explain the processing in the matrix
deriving part 122. First, the matrix deriving part 122 sets a
target area 24, in which the aircraft 110 may fly, near the flight
path 14. For example, the matrix deriving part 122 sets, as the
target area 24, a predetermined range on a horizontal plane derived
by extending the flight path 14 of the aircraft 110 horizontally as
shown in FIG. 5.
[0038] Next, the matrix deriving part 122 defines a virtual cloud
bottom surface 28 extending in a horizontal direction at an
altitude where the cloud bottom 10 has a large occupied area in a
target space 26 derived by projecting the target area 24 in the
vertical direction, based on the position, height, and size of the
cloud bottom 10 in the target space 26.
[0039] Then, the matrix deriving part 122 virtually sets electric
charges of the cloud bottom 10 on the assumption that the electric
charges are distributed only on the cloud bottom surface 28. For
example, the matrix deriving part 122 forms a mesh 30, divided
longitudinally and laterally at predetermined intervals
respectively, on the cloud bottom surface 28 in FIG. 5, and
temporarily sets electric charges lying on virtual points 32 which
are the intersection points of the mesh 30. At this time, the
respective electric charges at the virtual points 32 are
unknown.
[0040] The matrix deriving part 122 derives a coefficient matrix
based on the method of mirror charges (also known as the method of
images and the method of image charges), and the charge simulation
technique. Concretely, the matrix deriving part 122 defines the
ground surface 16 and the cloud bottom surface 28, as shown in the
longitudinal sectional view of FIG. 6. The electric charges 34a and
34b are assumed at the virtual points 32 on the cloud bottom
surface 28 respectively, and thereby an electric field arises at
each of the electric field sensors 112a and 112b on the ground
surface 16 due to the electric charges 34a and 34b. Here, two
virtual points 32 and two electric field sensors 112 will be
mentioned and described for convenience in explanation although
there are more than two virtual points 32 and more than two
electric field sensors 112.
[0041] Here, the ground surface 16 is considered as a conductor,
and the method of mirror charges by which the electric charge
density arising on the surface of a conductor is obtained by
defining virtual electric charges is adopted. For example, the
matrix deriving part 122 sets the ground surface 16 as the axis of
symmetry, defines a mirrored surface 36 line-symmetric to the cloud
bottom surface 28, and defines virtual electric charges 38a and 38b
lying on positions line-symmetric to the positions of the electric
charges 34a and 34b respectively. Note that, one electric charge
34a and one virtual electric charge 38a have the relation that the
sign of positive and negative is inverted to each other while the
other electric charge 34b and the other virtual electric charge 38b
have the relation that the sign of positive and negative is
inverted to each other.
[0042] In this case, Coulomb's force 40 shown by the solid arrows
(shown as 40a to 40h in FIG. 6) acts at the positions of the
electric field sensors 112a and 112b on the ground surface 16 due
to the electric charges 34a and 34b, and the virtual electric
charges 38a and 38b. Concretely, Coulomb's force 40a due to the
electric charge 34a, Coulomb's force 40b due to the electric charge
34b, Coulomb's force 40c due to the virtual electric charge 38a,
and Coulomb's force 40d due to the virtual electric charge 38b act
at the position of the electric field sensor 112a. Meanwhile,
Coulomb's force 40e due to the electric charge 34a, Coulomb's force
40f due to the electric charge 34b, Coulomb's force 40g due to the
virtual electric charge 38a, and Coulomb's force 40h due to the
virtual electric charge 38b act at the position of the electric
field sensor 112b.
[0043] The two kinds of the resultant force of the Coulomb's force
40 acting on the electric field sensors 112 become electric field
intensities 42a and 42b shown by the white arrows respectively.
When each of the electric field intensities 42a and 42b is
expressed by an integrated value of electric field intensities
corresponding to respective electric charges, based on the charge
simulation technique, the electric field intensities 42a and 42b
are each expressed by a linear algebraic equation as shown in FIG.
7.
[0044] In the linear algebraic equation of FIG. 7, the cloud bottom
altitude is the distance between the cloud bottom surface 28 and
the ground surface 16 while the point-to-point distance is the
distance between the virtual point 32 and the electric field sensor
112, as shown in FIG. 6. The CLOUD BOTTOM ALTITUDE/POINT-TO-POINT
DISTANCE shows component of the Coulomb's force 40 in an electric
field direction. The reason why the CLOUD BOTTOM
ALTITUDE/POINT-TO-POINT DISTANCE is doubled is because the
Coulomb's force 40 arises at the two positions of the electric
charge 34 and the virtual electric charge 38 per one electric
charge 34.
[0045] Since the electric charge 34 is line-symmetric to the
virtual electric charge 38 with respect to the axis of symmetry
consisting of the ground surface 16, the direction of the electric
field certainly becomes perpendicular to the ground surface 16 as
shown in FIG. 6. The matrix deriving part 122 derives the
coefficient matrix, to be multiplied by the respective electric
charges 34 on the cloud bottom surface 28, based on the linear
algebraic equation of FIG. 7.
[0046] When the electric field distribution 18 on the ground
surface 16 and the coefficient matrix have been specified as
described above, the electric charges 34 at the virtual points 32
should be derived by multiplying the electric field distribution 18
on the ground surface 16 by the inverse matrix of the coefficient
matrix. Nevertheless, the electric charge distribution 20 forming
the same electric field distribution 18 on the ground surface 16
can take a plurality of distributions, and therefore cannot be
derived simply. Accordingly, what is called a pseudo inverse matrix
that the concept of an inverse matrix in linear algebras is
generalized is used in the present implementation
(Pseudo Inverse Matrix Deriving Processing S104)
[0047] The pseudo inverse matrix deriving part 124 derives a pseudo
inverse matrix based on the coefficient matrix using a
technological calculation language, e.g., MATLAB (registered
trademark).
(Electric Charge Distribution Deriving Processing S106)
[0048] The electric charge distribution deriving part 126 derives
the electric charge distribution 20 on the cloud bottom surface 28
by multiplying the electric field distribution 18 on the ground
surface 16 by the pseudo inverse matrix obtained by the pseudo
inverse matrix deriving part 124.
[0049] Here, not a proper inverse matrix but the pseudo inverse
matrix has been used, and therefore the electric charge
distribution 20 may be distorted from original values. Accordingly,
the electric charge distribution deriving part 126 smoothes the
electric charge distribution 20 using a smoothing filter, e.g., a
convolution filter.
[0050] For example, the electric charge distribution deriving part
126 makes an average value of electric charges 34 in a virtual
point group, centering on a desired virtual point 32 and consisting
of longitudinal three points and lateral three points, to the
electric charge 34 at the desired virtual point 32 using a
convolution filter. The electric charge distribution deriving part
126 sequentially changes (sweeps) the desired virtual point 32, and
perform such smoothing processing for every desired virtual point
32. Although a convolution filter has been exemplified here, not
only a convolution filter but various smoothing filters may be
used
(Electric Field Distribution Deriving Processing S108)
[0051] The electric field distribution deriving part 128 derives
the electric field distribution on the ground surface 16 by
electrostatic analysis of the electric charge distribution 20
smoothed by the electric charge distribution deriving part 126. As
for the electrostatic analysis, existing desired technique can be
used, and therefore detailed explanation thereof is omitted
here.
[0052] In addition, the electric field distribution deriving part
128 calibrates absolute quantities changed due to the smoothing of
the electric charge distribution 20 by the electric charge
distribution deriving part 126. Concretely, the electric field
distribution deriving part 128 derives a proportional constant
which is a ratio between the derived electric field distribution on
the ground surface 16 and the electric field distribution 18 on the
ground surface 16 generated by the information acquisition part
120. The proportional constant can be expressed as (a peak value of
the electric field distribution 18 on the ground surface 16
generated by the information acquisition part 120)/(a peak value of
the derived electric field distribution on the ground surface 16),
for example. The proportional constant may be also derived based on
not only peak values but average values, median values or the
like.
[0053] The electric field distribution deriving part 128 corrects
the electric charge distribution 20 smoothed by the electric charge
distribution deriving part 126 by multiplying the smoothed electric
charge distribution 20 by the proportional constant. Then, the
electric field distribution deriving part. 128 derives electric
field distributions at various positions, based on the electric
charge distribution 20 which has been multiplied by the
proportional constant. For example, the electric field distribution
deriving part 128 derives an electric field distribution on the
flight path 14 of the aircraft 110, based on the electric charge
distribution 20 which has been multiplied by the proportional
constant.
(Information Transmission Processing S110)
[0054] The information transmission part 130 transmits, to the
aircraft 110, the electric field distribution 22 in an area
corresponding to the flight path 14 of the aircraft 110, out of the
electric field distributions derived by the electric field
distribution deriving part 128.
[0055] FIG. 8 and FIGS. 9A to 9D explain an example of calculation
in the electric field deriving processing. Here, MATLAB is used as
a technical calculation language. First, an electric field
distribution (E1) on the ground surface 16 is virtually set by
program codes (A) to (D) of FIG. 8. Concretely, the height, range,
mesh number and the like of the cloud bottom surface 28 are
initially set by the program code (A) of FIG. 8. Then, an electric
charge distribution (C0) that electric charges are disposed at two
positions is temporally set on the cloud bottom surface 28 by the
program code (B) of FIG. 8. Subsequently, a coefficient matrix (k)
in the linear algebraic equation between the electric field
distribution (E1) on the ground surface 16 and the electric charge
distribution (C0) is derived by the program code (C) of FIG. 8.
After that, an electric field distribution (E0) which is a product
of the coefficient matrix (k) and the electric charge distribution
(C0) is made to the electric field distribution (E1) on the ground
surface 16 by the program code (D) of FIG. 8. In this way, the
electric field distribution (E1) on the ground surface 16 is
virtually set.
[0056] When the electric field distribution (E1) on the ground
surface 16 set in this way is mapped on the ground surface 16,
electric field intensity as shown in FIG. 9A is derived. In the
figure, the electric field intensity becomes large as the position
is shifted from the upper left to the lower right. Here, it is
assumed that the information acquisition part 120 generated the
electric field distribution (E1) on the ground surface 16 while the
matrix deriving part 122 derived the coefficient matrix (k).
[0057] The pseudo inverse matrix deriving part 124 derives a pseudo
inverse matrix (pinv(k)) of the coefficient matrix (k) by the
function pinv of MATLAB. the electric charge distribution deriving
part 126 derives an electric charge distribution (C1) on the cloud
bottom surface 28 by multiplying the electric field distribution
(E1) on the ground surface 16 by the pseudo inverse matrix
(pinv(k)) of the coefficient matrix (k), by the program code (E) of
FIG. 8. When the electric charge distribution (C1) on the cloud
bottom surface 28 is mapped, Coulomb's force is shown as FIG. 9B.
In FIG. 9B, a negative electric charge has arisen at the upper left
while a positive electric charge has arisen at the lower right.
[0058] With reference to FIG. 9B, it can be understood that the
electric charge distribution (C1) on the cloud bottom surface 28 is
partially distorted. Accordingly, the electric charge distribution
deriving part 126 obtains a smoothed electric charge distribution
(C2) by convolution filter processing (filter 2) of the electric
charge distribution (C1) on the cloud bottom surface 28, by the
program code (F) of FIG. 8. In this way, the electric charge
distribution (C2) on which the electric charge changes smoothly can
be obtained as shown in FIG. 9C.
[0059] The electric field distribution deriving part 128 derives an
electric field distribution (E2) on the ground surface 16 based on
the smoothed electric charge distribution (C2), by the program code
(G) of FIG. 8. In this way, the electric field distribution (E2) on
the ground surface 16 is obtained as shown in FIG. 91). The
electric field distribution deriving part 128 derives a
proportional constant which is a ratio between the electric field
distribution (E1) acquired by the information acquisition part 120
and the derived electric field distribution (E2), by the program
code (H) of FIG. 8. The electric field distribution deriving part
128 multiplies the smoothed electric charge distribution (C2) by
the proportional constant, and then derives an electric field
distribution on the flight path 14 based on the electric charge
distribution (C2) which has been multiplied by the proportional
constant.
(Aircraft 110)
[0060] FIG. 10A and FIG. 10B show a schematic configuration of the
aircraft 110. The aircraft 110 includes a flight mechanism 150 and
a flight control system 152. The flight mechanism 150 has fixed
wings including main wings 150a, horizontal tail planes 150b and a
vertical tail 150c, and an internal combustion engine 150d (e.g., a
jet engine or a reciprocating engine) for obtaining thrust force.
The flight mechanism 150 generates lift around the wings by the
thrust force so that an airframe can keep floating in atmospheric
air.
[0061] The flight control system 152 is composed of a computer
including a CPU, a ROM storing programs and the like, a RAM as a
work area, and the like. The flight control system 152 receives
manipulated input by a pilot maneuvering the aircraft 110, and
controls the flight mechanism 150 to keep the aircraft 110 flying.
The flight control system 152 also functions as an information
transmission part 160, an information reception part 162, an
attitude control part 164 and a path correction part 166, by
collaborating with programs. Here, configuration related to the
lightning strike avoidance which is an object of the present
implementation will be described while description about
configuration unrelated to the present implementation is
omitted.
[0062] The information transmission part 160 transmits, to the
ground system 114, the position of the aircraft 110 and the flight
path 14 along which the aircraft 110 is planned to fly in
predetermined time. The information reception part 162 receives the
electric field distribution 22 on the flight path 14 of the
aircraft 110. In this way, the intensity and direction of the
electric field on the flight path 14 can be grasped. The attitude
control part 164 controls the attitude of the aircraft 110 based on
the direction of the electric field so that the attitude of the
aircraft 110 may become one in which the probability of damage by
lightning lowers. The path correction part 166 corrects the flight
path 14 so that the attitude of the aircraft 110 derived by the
attitude control part 164 can be kept.
[0063] FIG. 11A and FIG. 11B explain the processing by the attitude
control part 164. When the electric field has arisen in an electric
field direction 70 as shown in FIG. 11A, for example, the attitude
control part 164 tilts the angle around the pitch axis (pitch
angle) by a degrees so that a protruded plane 72 formed by parts of
the aircraft 110 protruded vertically upward may perpendicularly
intersect with the electric field direction 70. Meanwhile, when the
electric field has arisen in an electric field direction 70 as
shown in FIG. 11B, the attitude control part 164 tilts the angle
around the roll axis (roll angle) by .beta. degrees so that the
protruded plane 72 may perpendicularly intersect with the electric
field direction 70. In this way, the electric field intensity at
each protruded part of the aircraft 110 can be equalized, and
thereby the possibility of lightning strike due to the aircraft 110
as a trigger can be reduced.
[0064] In the present implementation, the electric field not only
in the vicinity of the aircraft 110 but on the whole flight path 14
along which the aircraft 110 is planned to fly is estimated, and
therefore the flight path 14 on which thunder can be avoided can be
derived more accurately to reduce the probability of damage by
lightning. In addition, the aircraft 110 can also change the
attitude according to the direction of the estimated electric field
on the whole flight path 14 to reduce the probability of damage by
lightning more.
[0065] Although a preferred implementation of the present invention
has been described above with reference to the accompanying
drawings, the present invention is not obviously limited to the
implementation. It is clear that a person skilled in the art can
arrive at various kinds of examples of changes and/or examples of
modifications within the description in claims, and they also
belong to the technical scope of the present invention
deservedly.
[0066] A program for making a computer function as respective
functional parts and a storage media, such as a flexible disk, a
magneto-optical disc, a ROM, a compact disc (CD), a digital
versatile disc (DVD), or a blu-ray disc (BD), which can be read by
a computer, storing the program are also provided. Here, a program
is a means for data processing described by a desired language and
description method.
[0067] Although an example of mounting the respective functional
parts in the ground system 114 and the aircraft 110 respectively
has been described in the above-mentioned implementation, a part or
all of the functional parts of the ground system 114 may work in
the aircraft 110 while a part or all of the functional parts of the
aircraft 110 may work in the ground system 114.
[0068] It is not necessary to process the respective processes, in
the electric field deriving processing in the present
specification, in time series in the order shown as the flow chart
necessarily. The respective processes may be processed in parallel
and include processing by a subroutine or subroutines.
* * * * *